Abstract 4437: BXQ-350: A novel biologic with an innovative mechanism of action targeting sphingolipid metabolism that induces cancer cell death and repolarizes the tumor microenvironment

Background: Antineoplastic agents seem to affect tumors by targeting cancer cells via cytotoxic mechanism (traditional cytotoxic agents), an oncogenic pathway that promotes cancer cells proliferation (targeted agents), or immune pathways that are dysregulated in the tumor microenvironment (immune checkpoint inhibitors -ICI-). Clinical results have demonstrated that ICIs led to significant clinical benefits and durable responses in patients that previously had no or limited therapeutic options. Clinical results also demonstrated that combining ICIs or ICI with cytotoxic/targeted agents improved response rate and duration of response. BXQ-350 is a novel biologic simultaneously leading to cancer cells death and rebalancing the tumor microenvironment by targeting sphingolipid metabolism that is dysregulated in cancer cells. Sphingosine-1-phosphate (S1P) is a signaling metabolite known to promote cancer cell survival and proliferation and to favor an immunosuppressor environment; ceramide is a metabolite known to induce cancer cell apoptosis, mitophagy or necrosis and to favor an immunoeffector environment.

Methods: BXQ-350 was investigated preclinically in different in vitro and in vivo models and clinically in a first-in-human Phase 1 safety and dose escalation study in cancer patients with recurrent advanced solid tumors.

Results: Preclinical results demonstrated that BXQ-350 targets sphingolipid metabolism, decreases S1P levels while it simultaneously increases ceramide levels, leading to cancer cells death across multiple cancer cell lines. By impacting S1P and ceramide, BXQ-350 is additive or synergistic with different classes of antineoplastic agents. In addition, ex vivo experiments demonstrated BXQ-350 modulates many of immune-effector/suppressor cells as it repolarizes macrophages towards the antitumoral M1 phenotype, inhibits differentiation and activity of immunosuppressor of MDSCs, and promotes the proliferation of CD4+ and CD8+ Tcells as well as their activity. Clinical results revealed that BXQ-350 was well tolerated in cancer patients and showed signs of single agent activity. Analyses of biomarker samples showed that in patients experiencing a clinical benefit, systemic S1P plasma levels decreased significantly, and ceramide levels increased. Analysis of circulating cytokines revealed that BXQ-350 seemed to induce an increase of antitumoral cytokines (IFNg, TNFa, IL-2) and a decrease in protumoral ones (IL-6, IL-8, IL-10).

Conclusions: Preclinical and clinical results demonstrated that BXQ-350 modulates sphingolipid metabolism leading to cancer cell death and stimulating the tumor microenvironment. Additional studies are ongoing to further understand BXQ-350’s MOA.

Citation Format: Gilles H. Tapolsky, Tim Stephens, Nikhil Wilkins, Robin Furnish, Charlie Cruze, Ray Takigiku. BXQ-350: A novel biologic with an innovative mechanism of action targeting sphingolipid metabolism that induces cancer cell death and repolarizes the tumor microenvironment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4437.

Abstract 3042: BXQ-350 may protect peripheral nerves from the direct cytotoxicity of chemotherapeutic agents leading to chemotherapy induced peripheral neuropathy

Background: Chemotherapy Induced Peripheral Neuropathy (CIPN) is a debilitating side effect associated with many antineoplastic chemotherapeutic agents including cytotoxic and targeted agents. It significantly impacts cancer patients’ quality of life during treatment, and may cause lasting neuropathy and shorten treatment regimen, potentially impacting clinical benefit. The pathology of CIPN is complex and still not completely understood. Damages to nerve cells are believed to be directly resulting from the antineoplastic agents’ cytotoxicity, and inflammation and the immune system are believed to be involved as well. Evidence suggests that intervention of certain GPCRs (e.g., cannabinoid receptors and others) may be useful as potential treatments. Altered neuronal sphingolipid metabolism has been linked to neuropathic pain and elevated plasma levels of sphingosine-1-phosphate (S1P) have also been associated with patients receiving chemotherapy and developing CIPN; therefore, modulating S1P levels may also be a potential treatment.

Method: BXQ-350 is a nanovesicle of Saposin C, an allosteric activator of sphingolipid metabolism, that lowers systemic S1P; Saposin C has been reported to activate certain GPCRs, including GPR37. BXQ-350 was investigated in an adult Phase 1 dose-escalation safety study in heavily pretreated all-comer cancer patients with advanced solid malignancies (NCT02859857). The cytoprotective properties of BXQ-350 against multiple agents known to induce CIPN were investigated in vitro in neuronal PC12 cells and BXQ-350’s CIPN mitigation properties were investigated in vivo in a CIPN preclinical model.

Results: A pancreatic cancer patient with chronic CIPN at time of enrollment in the Phase 1 study spontaneously reported a significant improvement of her neuropathic symptoms shortly after receiving BXQ-350; several patients had similar improvements. Results from preclinical experiments in PC12 cells revealed that BXQ-350 at concentration as low as 50 nM protected cells from oxaliplatin, paclitaxel, bortezomib or MMAE and promoted neurite growth. BXQ-350 was subsequently investigated in a murine oxaliplatin-induced CIPN preclinical model, showing a dose-dependent reduction of thermal and mechanical allodynia correlating with decreasing systemic S1P levels.

Conclusions: Preclinical results demonstrated that BXQ-350 was highly effective at protecting neuronal cells from antineoplastic agents known to induce CIPN and prevent CIPN in a preclinical model. These results appeared to support the clinical observation that BXQ-350 alleviated CIPN symptoms in several patients soon after receiving BXQ-350. Additional studies are on-going.

Citation Format: Nikhil Wilkins, Tim Stephens, Robin Furnish, Charlie Cruze, Darren Wolfe, Gilles H. Tapolsky, Ray Takigiku. BXQ-350 may protect peripheral nerves from the direct cytotoxicity of chemotherapeutic agents leading to chemotherapy induced peripheral neuropathy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3042.

BXQ-350 may alleviate symptoms of chemotherapy- induced peripheral neuropathy via modulation of S1P

93

Background: Chemotherapy Induced Peripheral Neuropathy (CIPN) is a debilitating side effect associated with many chemotherapeutic agents. It significantly impacts quality of life during treatment, causes lasting neuropathy, and may also shorten the treatment regimen, potentially impacting clinical benefit. The pathology of CIPN is still not completely understood, however, increasing evidence suggests sphingosine-1-phosphate (S1P) may be an important signaling molecule. Altered neuronal sphingolipid metabolism has been linked to neuropathic pain, evidenced by elevated plasma levels of S1P in patients receiving chemotherapy. Methods: BXQ-350 is a nanovesicle of Saposin C, an allosteric activator of sphingolipid metabolism, that lowers systemic S1P. BXQ-350 was investigated in an adult Phase 1 dose-escalation safety study in heavily pretreated all-comer cancer patients with advanced solid malignancies ( NCT02859857 ). The primary objective was to determine the safety profile and potential clinical activity of BXQ-350 as monotherapy. Samples were collected to explore potential biomarkers. Results: BXQ-350 was safe and well tolerated. Clinical signs of activity were observed in 13 patients (~17.8% of evaluable patients) experiencing a clinical benefit (PR, SD) up to cycle 6 and beyond including: 4 CRC, 1 pancreatic, and 1 GIST patient. Two patients are still on study six years after enrollment, including 1 CRC. Interestingly, a pancreatic cancer patient with chronic CIPN at time of enrollment spontaneously reported a significant improvement of her neuropathic symptoms shortly after receiving BXQ-350. Investigation of potential improvements in patients with chronic CIPN at time of enrollment revealed that 4 out of 10 patients experienced an improvement of their symptoms that seemed to be associated with a decrease in S1P systemic levels following BXQ-350 administration. BXQ-350 was subsequently investigated in a murine oxaliplatin-CIPN preclinical model with results showing a dose-dependent prevention/resolution of CIPN correlating with decreasing systemic S1P levels. Conclusions: Results of this Phase 1 study in heavily pretreated patients shows that BXQ-350 was well tolerated and seems to generate a clinical benefit via modulation of S1P. There were preliminary signs that BXQ-350 may alleviate symptoms of CIPN in relation to decreasing S1P concentration. Additional studies are underway to better understand this novel mechanism of action. Clinical trial information: 02859857 .

BXQ-350: Modulating ceramide and sphingosine-1-phosphate for antitumor activity in patients with advanced CRC

154

Background: Sphingolipids are a class of bioactive signaling molecules implicated in multiple cellular processes and molecular pathways. Many publications have demonstrated that ceramides are proapoptotic, synergize with cancer treatments, and mitigate chemoresistance. Findings also demonstrated that sphingosine-1-phosphate (S1P) is a key sphingolipid that promotes cancer cell proliferation, activates multiple oncogenic pathways, and stimulates immuno-suppressor cell populations promoting a pro-tumoral microenvironment. Several studies of colorectal cancer patients have shown high levels of ceramides being associated with improved survival, while high S1P levels are associated with a poor prognosis. Hence, modulation of sphingolipid metabolism continues to be a promising treatment approach. Methods: BXQ-350 is a nanovesicle of Saposin C, an allosteric activator of sphingolipid metabolism, that lowers systemic S1P and increases C18 ceramide. BXQ-350 was investigated in a Phase 1 dose-escalation safety study in an all-comer cancer patients with advanced solid malignancies ( NCT02859857 ) to determine its safety profile and potential clinical activity as monotherapy. Samples were collected to explore potential biomarkers. Results: 13 patients (~17.8% of evaluable patients) had a clinical benefit up to cycle 6 (PR, SD), with the majority experiencing a decrease in systemic S1P levels and an increase in C18 levels. 8 patients (~11% of evaluable patients) had PFS > 6 months, with 2 patients still on study six years after enrollment. Analysis of plasma samples also revealed an increase in anti-tumoral cytokines (IFNg, TNFa, IL-2) and a decrease in pro-tumoral ones (IL-6, 8, 10). Among patients with PFS > 6 months, there were 4 recurrent CRC patients (1PR, 3SD): 1 patient had a PFS of ~12 months, 2 of ~18 months, and 1 is still on study after 6 years. Conclusions: Results of this Phase 1 study in heavily pretreated patients show BXQ-350 was well tolerated and seem to generate a clinical benefit in CRC patients via modulation of S1P and ceramides. A phase 2 trial of BXQ-350 in combination with FOLFOX/Bevacizumab in newly diagnosed mCRC is on-going with plans to further investigate this novel mechanism of action. Clinical trial information: 02859857 .

P11.03.B BXQ-350: Modulating ceramide and Sphingosine-1-Phosphate for anti-tumor activity and potential mitigation of chemotherapy induced peripheral neuropathy

Background

Sphingolipids are a class of bioactive signaling molecules implicated in multiple cellular processes and molecular pathways. Many publications have indicated that among these sphingolipids, sphingosine-1-phosphate (S1P) is a key sphingolipid that promotes cancer cell survival and proliferation, activates multiple oncogenic pathways, and stimulates immuno-suppressor cell populations promoting a pro-tumoral microenvironment. Many of these publications have also implicated S1P with chemotherapy induced peripheral neuropathy, a debilitating and serious side effect that may impact therapeutic treatments and patient’s quality of life.

Material and Methods

BXQ-350 is a nanovesicle of Saposin C, an allosteric activator of sphingolipid metabolism, that has broad anticancer activity, potentially in part by lowering systemic S1P levels. BXQ-350 was investigated in a Phase 1 dose-escalation safety study in an all-comer cancer patients with advanced solid malignancies, including CNS tumors (NCT02859857) to determine its safety profile and its potential clinical activity as a single agent in cancer patients. Samples were collected to determine pharmacokinetics and explore potential biomarkers.

Results

11 patients (~15% of evaluable patients) with advanced disease had a clinical benefit and amongst these, 8 patients (~11% of evaluable patients) had PFS> 6 months with 2 patients still on study five years after enrollment. Analysis of patient’s samples revealed that BXQ-350 decreases systemic S1P levels in the majority of the patients experiencing a clinical benefit. In addition, several patients with established CIPN spontaneously reported improvements of their symptoms shortly after BXQ-350 administration. Analysis of these patients’ samples also revealed that S1P systemic levels had decreased, as well as pro-inflammatory cytokines associated with CIPN.

Conclusion

While these results are exploratory and preliminary in nature, they suggest that BXQ-350’s mechanism of action may represent a novel anti-cancer approach that may also mitigate CIPN.

EPEN-14. A Phase 1, Safety and Dose Escalation Study of BXQ-350 in Patients with Advanced Solid Malignancies Demonstrates that BXQ-350 is Well Tolerated and Shows Signs of Potential Clinical Activity in Ependymoma Patients

The significance of a dysregulated sphingolipid metabolism in cancer, including brain tumors, has been demonstrated and several enzymes involved in sphingolipid metabolism are being investigated as novel therapeutic targets for adult and pediatric brain cancers. Saposin C (Sphingolipid Activator PrO[S]etIN) is a human protein encoded by the Psap gene and is an allosteric activator of several enzymes involved in sphingolipid/ceramide metabolism. BXQ-350 is a nanovesicle of Saposin C that has broad anticancer activity, selectively inducing apoptosis of cancer cells by lowering Sphingosine-1-Phosphate and increasing ceramides concentrations and inducing an anti-tumoral immune response. BXQ-350 was investigated in a Phase 1 dose-escalation safety study in cancer patients with advanced solid malignancies including brain tumors (NCT02859857). The primary objective of this single agent study was to describe the safety profile and to determine the maximum tolerated dose, or the biological effective dose, of BXQ-350 administered intravenously at escalating doses from 0.7 mg/kg up to 2.4 mg/kg. Multiple secondary parameters were included to characterize BXQ-350’s pharmacokinetic parameters, efficacy profile and potential biomarkers. This trial was performed at four US sites. Results indicate that BXQ-350 was safe and well-tolerated as no DLT was observed and an MTD was not reached. RANO or RECIST 1.1 criteria were used to evaluate tumor response. Analysis of plasma samples suggests that BXQ-350 modulates sphingolipid metabolism and impacts the immune system positively. Furthermore, potential signs of single agent activity were observed across tumor types, including in two ependymomas for which results will be presented.

DIPG-30. A Phase 1, Safety and Dose Escalation Study of BXQ-350 in Combination with Radiation in Pediatric Patients with Diffuse Midline Glioma or Diffuse Intrinsic Pontine Glioma

The significance of sphingolipid metabolism in brain cancers has been demonstrated and enzymes involved in sphingolipid metabolism are being investigated as novel therapeutic targets for adult and pediatric brain cancers. Saposin C is a human protein encoded by the Psap gene and is an allosteric activator of enzymes involved in sphingolipid/ceramide metabolism. BXQ-350 is a nanovesicle of Saposin C that has broad anticancer activity, inducing apoptosis of cancer cells and an anti-tumoral immune response by lowering Sphingosine-1-Phosphate and increasing ceramides concentrations. Also, BXQ-350 is synergistic with radiation therapy. BXQ-350 was investigated in a Phase 1 dose-escalation safety study in pediatric brain cancer patients (NCT03967093); results showed that it was well-tolerated, a MTD was not established, and the safety profile warranted the investigation of combination studies at the highest dose tested (3.4 mg/kg). Additionally, results from a Phase 1 safety and dose escalation study in adult patients with advanced solid malignancies (NCT02859857) indicated that BXQ-350 was well tolerated and showed single agent activity with evidence of modulating sphingolipid metabolism and impacting the immune system positively. The primary objective of this dose-escalation study is to describe the safety profile and to determine the maximum tolerated dose of BXQ-350 in combination with radiation. BXQ-350 is administered intravenously in a modified Fibonacci cohort-based dose escalation design starting at 2.4mg/kg. Multiple secondary parameters are included to characterize BXQ-350’s pharmacokinetic parameters, efficacy profile and investigate potential biomarkers. This trial is currently enrolling at 3 US sites; as of January 2022, enrollment of cohort 1 (2.4 mg/kg and 54 Gy) has been completed while enrollment in cohort 2 (3.2 mg/kg and 54 Gy) is on-going. To this date, no dose-limiting toxicity has been observed and the combination BXQ-350 plus radiation has been well tolerated. Current results will be presented.

A phase 1, safety and dose escalation study of BXQ-350, a nanovesicle formulation of saposin c, a modulator of sphingolipid metabolism, in patients with advanced solid malignancies

e15059

Background: Bexion recently completed an all-comer Phase 1 clinical study of BXQ-350 in patients with advanced solid tumors including high grade gliomas to evaluate the safety profile and to determine the maximum tolerated- or biologically effective dose. BXQ-350 is a nanovesicle comprised of recombinantly expressed Saposin C (SapC) and dioleoylphosphatidylserine. SapC, a human protein encoded by the Psap gene, is an allosteric activator of several enzymes involved sphingolipid metabolism. Sphingolipids are bioactive signaling molecules implicated in multiple cellular processes including apoptosis and immune stimulation/inhibition. In nonclinical studies, BXQ-350 evidences broad anticancer activity, selectively inducing apoptosis of cancer cells by modulating sphingolipids (ceramides/S1P), and BXQ-350 acts synergistically with multiple classes of anticancer agents and treatments. Methods: In the trial (NTC02859857), performed at four US sites, BXQ-350 was administered intravenously for a minimum of 6 cycles over 28 weeks at escalating doses from 0.7 mg/kg up to 2.4 mg/kg. Multiple secondary parameters were included to characterize its pharmacokinetics, efficacy profile and identify potential biomarkers. Results: Results indicate that: i) BXQ-350 was safe and well-tolerated as no DLT was observed and an MTD was not reached; ii) treatment related adverse events leading to discontinuation were typical for this patient population and disease related; iii)* biomarker analyses suggest positive modulation of sphingolipid metabolism and stimulation of the immune system; iv)* surprisingly, some patients noted improvement of existing peripheral neuropathies. RANO or RECIST ver 1.1 criteria were used to evaluate tumor response: 13 patients reached Cycle 6 restaging (17% ORR); 8 patients (11.0% of evaluable patients) demonstrated progression free survival over more than 6 months; and 2 patients (a GBM and CRC patient) are still on study after 5 years. * subject of separate abstracts. Conclusions: In conclusion, BXQ-350 is a first-in-human and first-in-class novel biologic whose Phase 1 results suggest that it may have clinical utility either as a monotherapy or when combined with other targeted agents. Clinical trial information: 028559857.

Bedside to benchtop translational development: Targeting the S1P/ceramide axis may alleviate symptoms of chemical induced peripheral neuropathy

e15045

Background: Chemical Induced Peripheral Neuropathy (CIPN) is a debilitating and serious side-effect associated with many chemotherapeutic treatments. Often, CIPN is a dose-limiting toxicity, and its effects can be long-lasting in some patients. The pathology of CIPN is thought to involve not only cytotoxicity of neuronal cells, but also inflammation and immune responses. Hence, it is not surprising that the sphingolipid sphingosine-1-phosphate (S1P) is thought to be a key contributor to CIPN. Methods: BXQ-350, a nanovesicle comprised of recombinantly expressed Saposin C and dioleoylphosphatidylserine, has broad anticancer activity. It modulates sphingolipid metabolism and signaling, lowers S1P and increases pro-apoptotic ceramides, and induces an anti-tumoral immune response. BXQ-350 was investigated in a Phase 1 dose-escalation safety study of all-comer cancer patients with advanced solid malignancies, including high grade gliomas ( NCT02859857 )*. Multiple secondary parameters were included to characterize BXQ-350’s pharmacokinetics, efficacy profile and to elucidate potential biomarkers. Results: Interestingly, several patients with established CIPN spontaneously reported improvement of their neuropathy-related symptoms following BXQ-350 administration. Plasma samples from those patients revealed changes in circulating levels of sphingolipids and cytokines, including reduction of circulating levels of S1P and of IL-6, IL-8, cytokines, following BXQ-350 dosing. These properties of BXQ-350 were subsequently investigated in a murine oxaliplatin-CIPN preclinical model; results showed a dose-dependent prevention/resolution of CIPN, which also correlated with decreasing systemic S1P levels. Additional plasma based CIPN specific biomarkers were investigated, and preclinical results suggest that BXQ-350 may also favorably inhibit specific immune cells that favor CPIN. Conclusions: These preclinical and clinical observations related to CIPN, coupled with the fact that BXQ-350 acts synergistically with many chemotherapies and radiation, warrant further its investigation into preventing or improving CIPN related symptoms in cancer patients. Clinical trial information: 02859857.

S1P/ceramides and cytokines as potential biomarkers of response following administration of bxq-350

e15007

Background: BXQ-350 was investigated in a Phase 1 dose-escalation safety study of all-comer cancer patients with advanced solid malignancies, including high grade gliomas ( NCT02859857 ) (safety/efficacy results reported in a separate abstract). The primary objective of this single agent study was to describe the safety profile and to determine the maximum tolerated dose. Multiple secondary parameters were included to characterize BXQ-350’s pharmacokinetic parameters, efficacy profile and elucidation of potential biomarkers. BXQ-350 is a nanovesicle of recombinantly expressed Saposin C (SapC) and dioleoylphosphatidylserine. In nature, SapC is a protein encoded by the Psap gene, and serves as an allosteric activator of several enzymes involved in sphingolipid/ceramide metabolism, enzymes which are being investigated as novel therapeutic targets in cancers. Indeed, sphingolipids are a class of bioactive signaling molecules implicated in multiple cellular processes and molecular pathways. Amongst these sphingolipids, Sphingosine-1-Phosphate (S1P) induces cancer cell survival and proliferation, activates multiple oncogenic pathways, and promotes a pro-tumoral microenvironment. SapC has broad anticancer activity, lowering S1P and increasing ceramides, also inducing an anti-tumoral immune response. Methods: Lipodomic analysis (sphingolipids) and cytokines were analyzed in plasma samples of a subset of patients enrolled in this study. Results: Analysis of plasma biomarker samples, collected throughout the period patients were on study, reveals notable changes of circulating sphingolipids and cytokines. A subset of patients exhibited clinical benefits following BXQ-350 administration (see other presentation for details; ̃17% of the evaluable patients remained on study up to Cycle 6; and 8 patients (̃11%) with PFS> 6 months). Concomitant circulating changes in S1P and other ceramides may be indicative of treatment effect. Also, concurrent changes in circulating levels of pro/antitumoral cytokines were noted. Conclusions: While these results are exploratory and preliminary in nature, these initial results warrant further investigation. These observations will be further explored in specific cancer and non-cancer indications. Clinical trial information: 02859857.

Imaging of brain tumors with paramagnetic vesicles targeted to phosphatidylserine

PURPOSE

To investigate paramagnetic saposin C and dioleylphosphatidylserine (SapC-DOPS) vesicles as a targeted contrast agent for imaging phosphatidylserine (PS) expressed by glioblastoma multiforme (GBM) tumors.

MATERIALS AND METHODS

Gd-DTPA-BSA/SapC-DOPS vesicles were formulated, and the vesicle diameter and relaxivity were measured. Targeting of Gd-DTPA-BSA/SapC-DOPS vesicles to tumor cells in vitro and in vivo was compared with nontargeted paramagnetic vesicles (lacking SapC). Mice with GBM brain tumors were imaged at 3, 10, 20, and 24 h postinjection to measure the relaxation rate (R1) in the tumor and the normal brain.

RESULTS

The mean diameter of vesicles was 175 nm, and the relaxivity at 7 Tesla was 3.32 (s*mM)(-1) relative to the gadolinium concentration. Gd-DTPA-BSA/SapC-DOPS vesicles targeted cultured cancer cells, leading to an increased R1 and gadolinium level in the cells. In vivo, Gd-DTPA-BSA/SapC-DOPS vesicles produced a 9% increase in the R1 of GBM brain tumors in mice 10 h postinjection, but only minimal changes (1.2% increase) in the normal brain. Nontargeted paramagnetic vesicles yielded minimal change in the tumor R1 at 10 h postinjection (1.3%).

CONCLUSION

These experiments demonstrate that Gd-DTPA-BSA/SapC-DOPS vesicles can selectively target implanted brain tumors in vivo, providing noninvasive mapping of the cancer biomarker PS.

Direct pharmaceutical analysis of bisphosphonates by capillary electrophoresis

Bisphosphonate compounds have been studied as a class of potential drugs for the treatment of various bone diseases. However, the analyses of these compounds are problematic because most of them do not contain strong chromophores. Based on the unique structures of these compounds, we have employed a capillary electrophoresis (CE) technique for the characterization of these compounds in pharmaceutical dosage formulations. In this study, two CE methods were developed for the determination of a bisphosphonate compound, 2-thioethane-1,1-bisphosphonic acid. The first method involved the use of an uncoated column, a phosphate buffer, and hydrostatic injection with direct UV absorbance detection. The method showed excellent resolution and precision with a reasonable detection limit of 30 microg/ml. Sensitivity was further improved using a glycerol-coated column, together with a phosphate buffer of higher concentration and electrokinetic injection under sample stacking conditions. This modified method revealed a significant improvement in sensitivity with a detection limit of about 50 ng/ml. Both methods demonstrated high simplicity and excellent reproducibility and were successfully applied to the quantitative analyses of pharmaceutical dosing solutions.

Macrophage inflammatory proteins 1 and 2: expression by rat alveolar macrophages, fibroblasts, and epithelial cells and in rat lung after mineral dust exposure

Macrophage inflammatory proteins 1 alpha and 2 (MIP-1 alpha, MIP-2) are members of a growing family of cytokines thought to play a role in host defense. MIP-1 alpha and MIP-2 were previously identified in the mouse and shown to stimulate inflammatory cell recruitment. To better understand the potential role of MIP-1 alpha and MIP-2 in lung defense, we investigated the ability of rat lung cells to express mRNA for and/or secrete MIP-1 alpha and MIP-2 proteins in vitro and characterized expression of these cytokines in rat lung after in vivo exposure to silica (SiO2) or titanium dioxide (TiO2). In response to lipopolysaccharide, rat alveolar macrophages expressed increased levels of MIP-1 alpha and MIP-2 mRNA and secreted proteins (identified by N-terminal sequencing) homologous to mouse MIP-1 alpha and MIP-2. Rat alveolar macrophage MIP-1 alpha and MIP-2 mRNA expression was also increased by tumor necrosis factor-alpha (TNF) and adherence to plastic. Studies with a rat fibroblast and epithelial cell line demonstrated that MIP-2, but not MIP-1 alpha, expression can be detected in these cells after stimulation with TNF. Intratracheal instillation studies with SiO2 and TiO2 showed that inflammatory doses of these dusts increase MIP-1 alpha and MIP-2 mRNA expression in whole lung and that increased gene expression preceded the accumulation of inflammatory cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Matrix-assisted laser desorption mass spectrometry of proteins isolated by capillary zone electrophoresis

A simple method for the off-line coupling of laser desorption mass spectrometry (LDMS) and capillary zone electrophoresis (CZE) is described. Representative mass spectra of subpicomole quantities of proteins isolated from CZE are presented and discussed. The current detection limit for bovine alpha-lactalbumin is 100 fmols injected onto the CZE column. Horse heart myoglobin was demonstrated to be stable in CHES/KCl, a CZE buffer, for at least 1 month, suggesting that some isolates can be safely stored for long time periods prior to LDMS analysis. Protein stability in 0.1% aqueous trifluoroacetic acid (TFA), a common solvent for LDMS, must also be considered. In the special case of porcine pepsinogen, significant (greater than 50%) degradation was observed within 5 min in TFA. In favorable cases, mass measurement accuracies of +/- 0.02% were obtained for protein isolates. Factors limiting mass measurement accuracy are presented. Finally, the possibility of identifying protein isolates, by combining N-terminal sequencing, molecular mass measurements, and selective peptide "mapping" procedures, is discussed.

Design of a gas chromatograph with parallel radioactivity and mass spectrometric detection. Application to the identification of the major metabolite of d-limonene associated with alpha 2u-globulin

A Perkin Elmer 3920 gas chromatograph, equipped with a versatile inlet system (i.e. an injector/trap), was interfaced to a radioactivity detector and a mass-selective detector (H/P 5970B) to identify 14C-labeled compounds. The use of a pre-trap as a demountable, programmable-temperature injector, in conjunction with the injector/trap, allowed the introduction of 0.5-ml samples of rat kidney cytosol extracts to 0.32 mm I.D. capillary columns. The instrumentation greatly facilitated the identification of the major radiolabeled metabolite of d-limonene associated with the male rat-specific protein alpha 2u-globulin as 1,2-cis-d-limonene oxide.

d-Limonene-induced male rat-specific nephrotoxicity: evaluation of the association between d-limonene and alpha 2u-globulin

d-Limonene is a naturally occurring monoterpene, which when dosed orally, causes a male rat-specific nephrotoxicity manifested acutely as the exacerbation of protein droplets in proximal tubule cells. Experiments were conducted to examine the retention of [14C]d-limonene in male and female rat kidney, to determine whether d-limonene or one or more of its metabolites associates with the male rat-specific protein, alpha 2u-globulin, and if so, to identify the bound material. The results indicated that, 24 hr after oral administration of 3 mmol d-limonene/kg, the renal concentration of d-limonene equivalents was approximately 2.5 times higher in male rats than in female rats. Equilibrium dialysis in the presence or absence of sodium dodecyl sulfate indicated that approximately 40% of the d-limonene equivalents in male rat kidney associated with proteins in a reversible manner, whereas no significant association was observed between d-limonene equivalents and female rat kidney proteins. Association between d-limonene and male rat kidney proteins was characterized by high-performance gel filtration and reverse-phase chromatography. Gel filtration HPLC indicated that d-limonene in male rat kidney is associated with a protein fraction having a molecular weight of approximately 20,000. Separation of alpha 2u-globulin from other kidney proteins by reverse-phase HPLC indicated that d-limonene associated with a protein present only in male rat kidney which was definitively identified as alpha 2u-globulin by amino acid sequencing. The major metabolite associated with alpha 2u-globulin was d-limonene-1,2-oxide. Parent d-limonene was also identified as a minor component in the alpha 2u-globulin fraction. Thus, d-limonene, and more specifically d-limonene-1,2-oxide, associates with alpha 2u-globulin in a reversible manner in male rat kidney. This interaction may be responsible for excessive accumulation of alpha 2u-globulin in kidneys of male rats exposed to d-limonene.

The post-Paleozoic chronology and mechanism of 13C depletion in primary marine organic matter

Carbon-isotopic compositions of geoporphyrins have been measured from marine sediments of Mesozoic and Cenozoic age in order to elucidate the timing and extent of depletion of 13C in marine primary producers. These results indicate that the difference in isotopic composition of coeval marine carbonates and marine primary photosynthate was approximately 5 to 7 permil greater during the Mesozoic and early Cenozoic than at present. In contrast to the isotopic record of marine primary producers, isotopic compositions of terrestrial organic materials have remained approximately constant for this same interval of time. This difference in the isotopic records of marine and terrestrial organic matter is considered in terms of the mechanisms controlling the isotopic fractionation associated with photosynthetic fixation of carbon. We show that the decreased isotopic fractionation between marine carbonates and organic matter from the Early to mid-Cenozoic may record variations in the abundance of atmospheric CO2.

Carbon isotope fractionation by thermophilic phototrophic sulfur bacteria: evidence for autotrophic growth in natural populations

Purple phototrophic bacteria of the genus Chromatium can grow as either photoautotrophs or photoheterotrophs. To determine the growth mode of the thermophilic Chromatium species, Chromatium tepidum, under in situ conditions, we have examined the carbon isotope fractionation patterns in laboratory cultures of this organism and in mats of C. tepidum which develop in sulfide thermal springs in Yellowstone National Park. Isotopic analysis (13C/12C) of total carbon, carotenoid pigments, and bacteriochlorophyll from photoautotrophically grown cultures of C. tepidum yielded 13C fractionation factors near -20%. Cells of C. tepidum grown on excess acetate, wherein synthesis of the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase ribulose bisphosphate carboxylase) was greatly repressed, were isotopically heavier, fractionation factors of ca. -7% being observed. Fractionation factors determined by isotopic analyses of cells and pigment fractions of natural populations of C. tepidum growing in three different sulfide thermal springs in Yellowstone National Park were approximately -20%, indicating that this purple sulfur bacterium grows as a photoautotroph in nature.

An isotopic study of biogeochemical relationships between carbonates and organic carbon in the Greenhorn Formation

Carbon-isotopic compositions of total carbonate, inoceramid carbonate, micritic carbonate, secondary cements, total organic carbon, and geoporphyrins have been measured in 76 different beds within a 17-m interval of a core through the Greenhorn Formation, an interbedded limestone and calcareous shale unit of Cretaceous age (Cenomanian-Turonian) from the Western Interior Seaway of North America. Results are considered in terms of variations in the processes of primary production (which led to the biosynthesis of the molecular precursors of the geoporphyrins) and in secondary processes (those mediating the transformation of primary organic material into sedimentary total organic carbon). It is shown that the porphyrin isotopic record reflects primary isotopic variations more closely than the TOC isotopic record, and that, in these sediments, TOC is enriched in 13C relative to its primary precursor by 0.6 to 2.8%. This enrichment is attributed to isotope effects within the consumer foodweb and is associated with respiratory heterotrophy. Variations in this secondary enrichment are correlated with variations in the isotopic composition of marine carbonate. This correlation is attributed to effects of environmental changes on the marine foodweb. These may have included increased atmospheric oxygen associated with the Cenomanian-Turonian oceanic anoxic event. The isotopic fractionation associated with fixation of carbon by primary producers is observed to have varied by 1.5% during the interval of deposition. It is suggested that this change is due to a variation in the makeup of the community of primary producers and/or to a decrease in the atmospheric abundance of CO2 during the oceanic anoxic event.

Isotopic compositions and probable origins of organic molecules in the Eocene Messel shale

The sediments that now comprise the Messel shale accumulated 47 +/- 2 million years ago in anaerobic waters at the bottom of a lake. Subsequent depths of burial have not exceeded 300 m, nor has the temperature of the shale exceeded 40 degrees C. Contents of organic carbon reach 25%, and preservation of molecular structures has been excellent. Sixteen different geoporphyrins, including three derived from bacteriochlorophylls of the d series and thus indicative of the existence in the lake of an anaerobic photic zone, have been isolated and identified. Here, we show that the carbon isotopic compositions of these and other biomarkers allow identification of specific sources for some materials and reconstruction of carbon flows within the lake and its sediments. The 13C content of organic matter synthesized by lacustrine primary producers can be estimated from the observed 13C content of the geoporphyrins derived from their chlorophylls. Total organic material in the shale is depleted in 13C by six parts per thousand relative to that input. This difference cannot be explained by selective loss of components enriched in 13C, nor, as shown by isotopic compositions of other biomarkers, by inputs from land plants surrounding the lake or from methanogenic bacteria.